Pancreatic adenocarcinoma (PAC) is a fatal disease with no effective treatment. Clearly new means of detection and new approaches to treatment are urgently needed. It is increasingly recognized that the tumor microenvironment plays a key role in cancer. Pancreatic cancer has a very pronounced and abundant fibrosis (stroma) that it shares with the disease chronic pancreatitis. We have recently isolated the stroma cell in human PAC (pancreatic stellate cell, PSC) and found that it is an important contributor to tumor progression and renders cancer cells more resistant to chemotherapy and radiation. The PSC also increases growth and metastasis of pancreatic cancer in mice. Chronic pancreatitis (CP) is a known risk factor for PAC, however, the exact mechanism by which CP may lead to PAC is unknown. We hypothesize that the PSC, which is present in both CP and PAC, is the common link and contributes to both the fibrosis and inflammation in CP and the progression to early lesions of pancreatic cancer (PanIN) and invasive PAC. We will test this hypothesis using a novel genetically engineered mouse model of pancreatic cancer which displays all of the steps of PAC development: fibrosis and chronic pancreatitis at early stages, and PanINs and finally invasive PAC with metastasis at later stages. We will selectively destroy the PSCs in these mice by using a gene promoter that is specific for PSCs and forcing only these cells to express a receptor for Diphtheria toxin (DTR). When diphtheria toxin (DT) is given to the mice, all cells that express DTR will be eliminated. To determine the role of PSCs in the continuum of PAC development, we will administer diphtheria toxin to the genetically engineered mouse at different time points. For Specific Aim 1, we will determine whether PSCs are essential for the development of fibrosis in CP by giving Diphtheria toxin to the mice at early time points. The pancreas tissue of these mice will be examined for inflammation and CP, as well as subsequent development of PAC at later time points. For Specific Aim 2, the PSCs will be destroyed later by giving the toxin at later time points when PanIN lesions and invasive PAC should be developed. With this strategy, we will be able to determine whether PSCs have a critical role in development of pancreatic cancer. To date, a mouse model of pancreatic cancer that targets the stellate cells has not yet been reported. Using this innovative approach, we expect to gain a better understanding of the role of PSCs in the progression of pancreatic cancer. This knowledge will enable us to develop novel treatments for this disease that target the tumor microenvironment. PUBLIC HEALTH RELEVANCE: In this project, we will determine whether stellate cells in the tumor microenvironment are necessary for the development of pancreatic cancer. The results from this project will provide a greater understanding of how these cells contribute to early and late pancreatic cancer. This information provides valuable insight towards the development of novel treatments for pancreatic cancer, as well as possible approaches to early cancer detection and cancer prevention.